Radiolabeling of RGD peptide and preliminary biological evaluation in mice bearing U87MG tumors

摘要

2-[ 18F]Fluoroethyl azide ([ 18F]FEA) and terminal alkynyl modified propioloyl RGDfK were selected in this study. [ 18F]FEA was prepared by nucleophilic radiofluorination of 2-azidoethyl 4-toluenesulfonate with radiochemical yield of 71 ± 4% (n = 5, decay-corrected). We assessed the various conditions of the CuAAC reaction between [ 18F]FEA and propioloyl RGDfK, which included peptide concentration, reaction time, temperature and catalyst dosage. The 18F-labeled-RGD peptide ([ 18F]F-RGDfK) could be obtained in 60 min by a two-step radiochemical synthesis route, with total radiochemical yield of 60 ± 2% (n = 3, decay-corrected) through click chemistry. [ 18F]F-RGDfK showed high stability in phosphate buffered saline and new-born calf serum. Micro-PET imaging at 1 h post injection of [ 18F]F-RGDfK showed medium concentration of radioactivity in tumors while much decreased concentration in tumors in the blocking group. These results showed that [ 18F]F-RGDfK obtained by click chemistry maintained the affinity and specificity of the RGDfK peptide to integrin α vβ 3. This study provided useful information for peptide radiofluorination by using click chemistry.